The present invention generally relates to an electromechanical resonator and, more particularly, to a piezoelectric tuning fork device.
Various types of piezoelectric tuning fork devices have heretofore been available commercially, an example of which is shown in FIG. 1 of the accompanying drawings. Referring to FIG. 1, the prior art piezoelectric tuning fork device comprises a generally U-shaped tuning vibrator 1 formed by bending a strip of metallic material so as to provide a pair of opposed and juxtaposed prongs 2 and 3 which occupy the opposed leg portions of the shape of a Figure "U", respectively. Each of the prongs 2 and 3 has and electrode layer 6 or 7 deposited on and overlying a respective piezoelectric ceramic plate 4 or 5 bonded to either one of the external and internal surfaces, for example, the internal surface, of the corresponding prong 2 or 3.
The prior art piezoelectric tuning fork device described with reference to and shown in FIG. 1 involves some difficulties. Specifically, since the tuning vibrator 1 is formed by bending the metallic strip, there is a limit to the possible reduction in size of the piezoelectric tuning fork device. In addition, the employment of a bonding agent used to connect the piezoelectric ceramic plates 4 and 5 to the respective prongs 2 and 3 tends to adversely affect the performance of the piezoelectric tuning fork device itself to such an extent that the role and importance of the bonding agent cannot be ignored in designing such a device.
In view of the above described difficulties, the present inventors have devised a piezoelectric tuning fork device, such as shown in FIG. 2 of the accompanying drawings and disclosed in the copending United State patent application Ser. No. 902,819. The piezoelectric tuning fork device shown in FIG. 2 comprises a generally U-shaped tuning vibrator 10 formed by cutting a generally rectangular block of metal to provide a pair of opposed and juxtaposed prongs 11 and 12 which occupy the opposed leg portions of the shape of a figure "U", respectively. Each of the prongs 11 and 12 has an electrode layer 13 or 14 vapor-deposited on and overlying a respective piezoelectric layer 15 or 16 which is made of a piezoelectric material such as ZnO and which is deposited on an external surface of the corresponding prong 11 or 12 by the use of a known sputtering technique.
The piezoelectric tuning fork device described with reference to and shown in FIG. 2 can be manufactured in a size more compact than that shown in FIG. 1 and, as compared with the construction shown in FIG. 1, can be manufactured precisely on a mass production line, is simple in design and has relatively high physical strength.